Cooling unit of drive motor

ABSTRACT

A cooling unit of a drive motor includes: a fixing member installed on an inner wall surface of a motor housing and configured to fix a stator core of the drive motor, wherein the fixing member has a ring shape, includes a flow path formed therein in order to allow a cooling medium to flow, and includes a cooling medium inlet and a cooling medium outlet formed to be connected to the flow path, the flow path includes a first path connecting the cooling medium inlet and the cooling medium outlet to each other at one side and a second path connecting the cooling medium inlet and the cooling medium outlet to each other at another side, and the first and second paths have different flow cross sections and are connected to each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/264,767 filed on Sep. 14, 2016 which claims under 35 U.S.C. § 119(a)the benefit of Korean Patent Application No. 10-2016-0047095 filed inthe Korean Intellectual Property Office on Apr. 18, 2016, the entirecontents of which are incorporated herein by reference.

BACKGROUND (a) Technical Field

The present invention relates to a drive motor for a vehicle, moreparticularly, to a cooling unit of the drive motor capable of cooling astator core of the drive motor fixed within a housing.

(b) Description of the Related Art

Generally, an electric vehicle or a hybrid vehicle called anenvironmentally-friendly vehicle may be driven by an electric motor(hereinafter, referred to as a “drive motor”) obtaining a torque bypower of a battery.

The drive motor as described above includes a stator core. The statorcore is fixed within a housing, and a rotor is mounted integrally with amotor shaft of the drive motor.

Meanwhile, a large amount of heat is generated due to an eddy currentgenerated in the stator core of the drive motor, cooling should benecessarily performed in order to prevent damage due to the heat andsecure continuously stable operability.

Particularly, cooling of the drive motor such as a permanent magnetsynchronous motor (PMSM) plays a very important role in efficiency ofthe motor and protection of core components (a permanent magnet, awinding coil, and the like). In the drive motor, when a temperature ofthe permanent magnet becomes a predetermined level or more, permanentmagnet demagnetization is generated, such that intensity of magneticforce becomes weak, which has a significantly negative influence onefficiency of the motor.

For cooling the drive motor, an oil cooling scheme through oil and awater cooling scheme through a coolant have been mainly used. Amongthem, a cooling unit of the drive motor depending on the water coolingscheme will be described by way of example. In the cooling unit of thedrive motor depending on the water cooling scheme, a support ring forcooling a stator core simultaneously with fixing the stator core to ahousing is installed between the housing and the stator core.

In the related art, the support ring includes a coolant flow path formedtherein along a ring direction (a circumferential direction) in order toallow a coolant to flow. In addition, the support ring includes acoolant inlet formed in order to inject the coolant into the coolingflow path, and a coolant outlet formed in order to exhaust the coolantfrom the coolant flow path. Here, the coolant injected through thecoolant inlet may flow from the coolant inlet to both sides along thecoolant flow path, and be exhausted through the coolant outlet.

Therefore, the coolant flow path of the support ring may include a firstpath connecting the coolant inlet and the coolant outlet to each otherat one side and a second path connecting the coolant inlet and thecoolant outlet to each other at another side. Here, the coolant flowpath may include the first and second paths of which flowcross-sectional areas are the same as each other and lengths aredifferent from each other.

Therefore, in the coolant flow path of the support ring according to therelated art, the flow cross-sectional areas of the first and secondpaths are the same as each other and the lengths of the first and secondpaths are different from each other, such that a greater amount of flowrate may be introduced into a path having a shorter length, among thefirst and second paths.

Therefore, in the related art, imbalance of a flow rate of the coolantflowing along the first and second paths occurs in the coolant flow pathof the support ring, which may cause cooling imbalance of the drivemotor.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

The present invention provides a cooling unit of a drive motor havingadvantages of decreasing imbalance of a flow rate of a coolant flowingalong a coolant flow path of a support ring.

An exemplary embodiment of the present invention provides a cooling unitof a drive motor, including: a fixing member installed on an inner wallsurface of a motor housing and configured to fix a stator core of thedrive motor, wherein the fixing member has a ring shape, includes a flowpath formed therein in order to allow a cooling medium to flow, andincludes a cooling medium inlet and a cooling medium outlet formed to beconnected to the flow path, the flow path includes a first pathconnecting the cooling medium inlet and the cooling medium outlet toeach other at one side and a second path connecting the cooling mediuminlet and the cooling medium outlet to each other at another side, andthe first and second paths have different flow cross sections and areconnected to each other.

The first and second paths may have different lengths, and the firstpath may have a length longer than that of the second path.

The first path may have a flow cross section larger than that of thesecond path.

The first and second paths may allow the same flow rate of coolingmedium to flow.

Another exemplary embodiment of the present invention provides a coolingunit of a drive motor including: a fixing member installed on an innerwall surface of a motor housing and configured to fix a stator core ofthe drive motor, wherein the fixing member has a ring shape, includes aflow path formed therein in order to allow a cooling medium to flow, andincludes a cooling medium inlet and a cooling medium outlet formed to beconnected to the flow path, the flow path includes a first pathconnecting the cooling medium inlet and the cooling medium outlet toeach other at one side and a second path connecting the cooling mediuminlet and the cooling medium outlet to each other at another side, andthe first and second paths have different lengths, a plurality ofthrough-holes connected to the flow path are formed along an outercircumferential direction of the fixing member in an outercircumferential surface of the fixing member, and cap plugs areinstalled in the through-holes, and the cap plugs are inserted into thethrough-holes at different depths so as to each correspond to the firstand second paths.

The first and second paths may have the same flow cross section and beconnected to each other.

The first path may have a length longer than that of the second path.

An insertion depth of the cap plugs corresponding to the first path maybe shallower than that of the cap plugs corresponding to the secondpath.

Yet another exemplary embodiment of the present invention provides acooling unit of a drive motor including: a fixing member installed on aninner wall surface of a motor housing and configured to fix a statorcore of the drive motor, wherein the fixing member has a ring shape,includes a flow path formed therein in order to allow a cooling mediumto flow, and includes a cooling medium inlet and a cooling medium outletformed to be connected to the flow path, the flow path includes a firstpath connecting the cooling medium inlet and the cooling medium outletto each other at one side and a second path connecting the coolingmedium inlet and the cooling medium outlet to each other at anotherside, and the first and second paths have different lengths, a pluralityof through-holes connected to the flow path are formed along an outercircumferential direction of the fixing member in an outercircumferential surface of the fixing member, and cap plugs areinstalled in the through-holes, and the cap plugs are inserted into thethrough-holes at different depths so as to each correspond to the firstand second paths, and insertion depths of the cap plugs are varied byactuators.

The first and second paths may have the same flow cross section and beconnected to each other.

The first path may have a length longer than that of the second path.

An insertion depth of the cap plugs corresponding to the second path maybe deeper than that of the cap plugs corresponding to the first path.

The actuators may include operation cylinders connected to the cap plugscorresponding to the second path.

BRIEF DESCRIPTION OF THE DRAWINGS

A brief description of the drawings will be provided to moresufficiently understand the drawings which are used in the detaileddescription of the present invention.

FIG. 1 is a cross-sectional view schematically showing a cooling unit ofa drive motor according to an exemplary embodiment of the presentinvention.

FIG. 2 is a perspective view showing a fixing member used in the coolingunit of the drive motor according to an exemplary embodiment of thepresent invention.

FIG. 3 is a cross-sectional view showing the fixing member used in thecooling unit of the drive motor according to an exemplary embodiment ofthe present invention.

FIG. 4 is a cross-sectional view showing a fixing member used in acooling unit of a drive motor according to another exemplary embodimentof the present invention.

FIG. 5 is a cross-sectional view showing a fixing member used in acooling unit of a drive motor according to yet another exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g. fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. Throughout the specification, unless explicitly describedto the contrary, the word “comprise” and variations such as “comprises”or “comprising” will be understood to imply the inclusion of statedelements but not the exclusion of any other elements. In addition, theterms “unit”, “-er”, “-or”, and “module” described in the specificationmean units for processing at least one function and operation, and canbe implemented by hardware components or software components andcombinations thereof.

Further, the control logic of the present invention may be embodied asnon-transitory computer readable media on a computer readable mediumcontaining executable program instructions executed by a processor,controller or the like. Examples of computer readable media include, butare not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes,floppy disks, flash drives, smart cards and optical data storagedevices. The computer readable medium can also be distributed in networkcoupled computer systems so that the computer readable media is storedand executed in a distributed fashion, e.g., by a telematics server or aController Area Network (CAN).

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. As those skilled in the art would realize,the described embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.

FIG. 1 is a cross-sectional view schematically showing a cooling unit ofa drive motor according to an exemplary embodiment of the presentinvention.

Referring to FIG. 1, an exemplary embodiment of the present inventionmay be used in a drive motor 3 used in an electric vehicle or a hybridvehicle. The drive motor 3 may include a permanent magnet synchronousmotor (PMSM) or a wound rotor synchronous motor (WRSM).

The drive motor 3 includes a stator core 10 fixed within a motor housing1 (hereinafter, referred to as a “housing” for convenience) andgenerating a magnetic flux, and a rotor core 30 disposed to have apredetermined gap from the stator core 10 and be rotated around arotation shaft 20, which is a drive shaft. For example, the drive motor3 may be used in an inner rotor type synchronous motor in which therotor core 30 is disposed inside the stator core 10.

A cooling unit 100 of the drive motor 3 according to an exemplaryembodiment of the present invention as described above has a structurein which the stator core 10 of the drive motor 3 is fixed within thehousing 1, and the stator core 10 may be cooled by a cooling medium (forexample, a coolant).

In an exemplary embodiment of the present invention, the cooling unit100 of the drive motor 3 that may decrease imbalance of a flow rate ofthe cooling medium and further improve cooling performance for thestator core 10 of the drive motor 3 is provided.

To this end, the cooling unit 100 of the drive motor 3 according to anexemplary embodiment of the present invention includes a fixing member50 installed between the housing 1 and the stator core 10.

FIG. 2 is a perspective view showing a fixing member used in the coolingunit of the drive motor according to an exemplary embodiment of thepresent invention, and FIG. 3 is a cross-sectional view of FIG. 2.

Referring to FIGS. 1 to 3, in an exemplary embodiment of the presentinvention, the purpose of the fixing member 50 is to cool heat generatedin the stator core 10 through a coolant, which is a cooling medium, in awater cooling scheme, simultaneously with supporting and fixing thestator core 10 of the drive motor 3 within the housing 1.

The fixing member 50 is provided as a support ring of which an entireshape is a ring shape, and is installed between the housing 1 and thestator core 10. The fixing member 50 may be formed of a stainless steelmaterial having a thermal expansion coefficient similar to that of thestator core 10.

In an exemplary embodiment of the present invention, the fixing member50 includes a coolant flow path 61 allowing the coolant, which is thecooling medium, to flow in a ring direction (a circumferentialdirection) in order to cool the stator core 10. The coolant flow path 61may be formed integrally with the fixing member 50 within the fixingmember 50.

The fixing member 50 preferably is manufactured through core type lowpressure casting, and the coolant flow path 61 is formed integrally withthe fixing member 50 within the fixing member 50. That is, the coolantflow path 61 may be formed as an annular internal space within aring-shaped body of the fixing member 50 by molding the ring-shaped bodyof the fixing member 50 through the low pressure casting.

In addition, a plurality of through-holes 71 connected to the coolantflow path 61 are formed along an outer circumferential direction of thefixing member 50 in an outer circumferential surface of the fixingmember 50. The through-holes 71 are formed along a circumferentialdirection in the outer circumferential surface of the fixing member 50so as to be spaced apart from each other by predetermined intervals.

The through-holes 71 may be formed as core holes for forming the coolantflow path 61 within the fixing member 50. A cooling medium inlet 73 forinjecting the coolant into the coolant flow path 61 is formed in any oneof the through-holes 71. In addition, a cooling medium outlet 75 forexhausting the coolant from the coolant flow path 61 is formed inanother of the through-holes 71.

Cap plugs 77 (shown by an alternate long and short dash line in FIG. 3)for plugging the through-holes 71 are installed in through-holes otherthan the through-holes in which the cooling medium inlet 73 and thecooling medium outlet 75 are installed among the through-holes 71. Thecap plugs 77 plug the through-holes 71 while being inserted into thethrough-holes 71 in a press-fitting scheme.

Meanwhile, in an exemplary embodiment of the present invention, sincethe coolant flow path 61 to which the coolant flows is formed along thecircumferential direction (or the ring direction) of the fixing member50, the coolant flow path 61 includes a first path 81 and a second path82 connected to each other. The first and second paths 81 and 82 aredivided along the circumferential direction of the fixing member 50 andare connected to each other, thereby making it possible to form thecoolant flow path 61 described above.

The first path 81 connects the cooling medium inlet 73 and the coolingmedium outlet 75 to each other at one side on the basis of thecircumferential direction of the fixing member 50, and the second path82 connects the cooling medium inlet 73 and the cooling medium outlet 75to each other at another side on the basis of the circumferentialdirection of the fixing member 50.

The first and second paths 81 and 82 of the coolant flow path 61 areprovided with different lengths. For example, a length of the first path81 may be relatively longer than that of the second path 82.

In an exemplary embodiment of the present invention, the first andsecond paths 81 and 82 have different flow cross sections and areconnected to each other. For example, a flow cross section of the firstpath 81 is larger than that of the second path 82.

Therefore, in the cooling unit 100 of a drive motor according to anexemplary embodiment of the present invention configured as describedabove, the fixing member 50 is installed between the housing 1 and thestator core 10, and the coolant flow path 61 to which the coolant flowsis formed in the fixing member 50, thereby making it possible to allowthe coolant to flow to the coolant flow path 61 and cool heat generatedin the stator core 10 by the coolant.

In an exemplary embodiment of the present invention, the coolantinjected through the cooling medium inlet 73 of the fixing member 50 mayflow in two directions along the first and second paths 81 and 82 of thecoolant flow path 61, and be exhausted through the cooling medium outlet75.

Further, in an exemplary embodiment of the present invention, since thelength of the first path 81 is longer than that of the second path 82and the flow cross section of the first path 81 is larger than that ofthe second path 82, the first and second paths 81 and 82 may allow thesame flow rate of cooling medium to flow.

That is, since the second path 82 having a length relatively shorterthan that of the first path 81 has a flow cross section smaller thanthat of the first path 81, a flow velocity of the coolant is increasedin the second path 82 as compared with in the first path 81. Inaddition, since the first path 81 having a length relatively longer thanthat of the second path 82 has a flow cross section larger than that ofthe second path 82, a flow velocity of the coolant is decreased in thefirst path 81 as compared with in the second path 82.

Therefore, imbalance of the flow rate of the coolant flowing along thefirst and second paths 81 and 82 of the coolant flow path 61 isdecreased in an exemplary embodiment of the present invention ascompared with the related art in which flow cross sections of the firstand second paths are the same as each other and lengths of the first andsecond paths are different from each other. As a result, coolingperformance for the stator core 10 of the drive motor 3 may be improved.

FIG. 4 is a cross-sectional view showing a fixing member used in acooling unit of a drive motor according to another exemplary embodimentof the present invention.

Referring to FIG. 4, the cooling unit of a drive motor according toanother exemplary embodiment of the present invention may include afixing member 150 having a coolant flow path 161 of which flow crosssections of first and second paths 181 and 182 are the same as eachother and a length of the first path 181 is relatively longer than thatof the second path 182.

Further, the cooling unit of a drive motor according to anotherexemplary embodiment of the present invention may include cap plugs 177installed into through-holes 171 of the fixing member 150 at differentinsertion lengths so as to each correspond to the first and second paths181 and 182.

Here, the cap plugs 177 in the first path 181 are inserted into thethrough-holes 171 at an insertion depth shallower than that of the capplugs 177 in the second path 182. In addition, the cap plugs 177 in thesecond path 182 are inserted into the through-holes 171 at an insertiondepth deeper than that of the cap plugs 177 in the first path 181.

Therefore, in another exemplary embodiment of the present invention,since the cap plugs 177 in the second path 182 having a lengthrelatively shorter than that of the first path 181 are inserted into thethrough-holes 171 at an insertion depth deeper than that of the capplugs 177 in the first path 181, a flow velocity of the coolant isincreased in the second path 182 as compared with the first path 181.

In addition, in another exemplary embodiment of the present invention,since the cap plugs 177 in the first path 181 having a length relativelylonger than that of the second path 182 are inserted into thethrough-holes 171 at an insertion depth shallower than that of the capplugs 177 in the second path 182, a flow velocity of the coolant isdecreased in the first path 181 as compared with the second path 182.

Therefore, in another exemplary embodiment of the present invention,insertion depths of the cap plugs 177 each corresponding to the firstand second paths 181 and 182 of the coolant flow path 161 are set to bedifferent from each other, thereby decreasing imbalance of a flow rateof the coolant flowing along the first and second paths 181 and 182.Therefore, cooling performance for the stator core of the drive motormay be increased.

FIG. 5 is a cross-sectional view showing a fixing member used in acooling unit of a drive motor according to yet another exemplaryembodiment of the present invention.

Referring to FIG. 5, the cooling unit of a drive motor according to yetanother exemplary embodiment of the present invention may include afixing member 250 having a coolant flow path 261 of which flow crosssections of first and second paths 281 and 282 are the same as eachother and a length of the first path 281 is relatively longer than thatof the second path 282, similar to the cooling unit of a drive motoraccording to another exemplary embodiment of the present inventiondescribed above.

Further, the cooling unit of a drive motor according to yet anotherexemplary embodiment of the present invention may include cap plugs 277installed into through-holes 271 of the fixing member 250 at differentinsertion lengths so as to each correspond to the first and second paths281 and 282.

In yet another exemplary embodiment of the present invention, insertiondepths of the cap plugs 277 each corresponding to the first and secondpaths 281 and 282 may be varied by actuators 290.

For example, the cap plugs 277 in the second path 282 are inserted intothe through-holes 271 at an insertion depth deeper than that of the capplugs 277 in the first path 281 by the actuators 290.

Here, the cap plugs 277 in the first path 281 are inserted into thethrough-hole 271 at an insertion depth shallower than that of the capplugs 277 in the second path 282, for example, by a thickness of thethrough-holes 271.

The actuators 290 as described above may include, for example, operationcylinders 291 installed to be connected to the cap plugs 277corresponding to the second path 282 and well-known in the related art.

Therefore, since the cap plugs 277 in the second path 282 having alength relatively shorter than that of the first path 281 are insertedinto the through-holes 271 at an insertion depth deeper than that of thecap plugs 277 in the first path 281 by the actuators 290, a flowvelocity of the coolant is increased in the second path 282 as comparedwith in the first path 281.

In addition, since the cap plugs 277 in the first path 281 having alength relatively longer than that of the second path 282 are insertedinto the through-holes 271 at an insertion depth shallower than that ofthe cap plugs 277 in the second path 282, a flow velocity of the coolantis decreased in the first path 281 as compared with the second path 282.

Therefore, in yet another exemplary embodiment of the present invention,insertion depths of the cap plugs 277 each corresponding to the firstand second paths 281 and 282 of the coolant flow path 261 are set to bedifferent from each other through the actuators 290, thereby decreasingimbalance of a flow rate of the coolant flowing along the first andsecond paths 281 and 282 of the coolant flow part 261. Therefore,cooling performance for the stator core of the drive motor may beincreased.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A cooling unit of a drive motor, comprising: afixing member installed on an inner wall surface of a motor housing andconfigured to fix a stator core of the drive motor, wherein the fixingmember has a ring shape, includes a flow path formed therein in order toallow a cooling medium to flow, and includes a cooling medium inlet anda cooling medium outlet formed to be connected to the flow path, theflow path includes a first path connecting the cooling medium inlet andthe cooling medium outlet to each other at one side and a second pathconnecting the cooling medium inlet and the cooling medium outlet toeach other at another side, and the first and second paths havedifferent lengths, a plurality of through-holes connected to the flowpath are formed along an outer circumferential direction of the fixingmember in an outer circumferential surface of the fixing member, and capplugs are installed in the through-holes, and the cap plugs are insertedinto the through-holes at different depths so as to each correspond tothe first and second paths, and insertion depths of the cap plugs arevaried by actuators.
 2. The cooling unit of a drive motor of claim 1,wherein: the first and second paths have the same flow cross section andare connected to each other.
 3. The cooling unit of a drive motor ofclaim 2, wherein: the first path has a length longer than that of thesecond path.
 4. The cooling unit of a drive motor of claim 3, wherein:an insertion depth of the cap plugs corresponding to the second path isdeeper than that of the cap plugs corresponding to the first path. 5.The cooling unit of a drive motor of claim 4, wherein: the actuatorsinclude operation cylinders connected to the cap plugs corresponding tothe second path.